/*
 * Alloy Analyzer
 * Copyright (c) 2002 Massachusetts Institute of Technology
 *
 * The Alloy Analyzer is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * The Alloy Analyzer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with the Alloy Analyzer; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package alloy.transform;

import alloy.ast.ASTDepthFirstReplacer;
import alloy.ast.BinaryFormula;
import alloy.ast.ComprehensionExpr;
import alloy.ast.ImplicationFormula;
import alloy.ast.LogicOp;
import alloy.ast.NegFormula;
import alloy.ast.Node;

/**
 * EqDepthFirstReplacer prevents its superclass from visiting AST nodes on which
 * equality reasoning cannot be performed.
 **/
class EqDepthFirstReplacer extends ASTDepthFirstReplacer {

   
    public Object visit(BinaryFormula binaryFormula_) {
		// can't do eq reasoning inside an OR or an IFF .. .
		if (!binaryFormula_.getOp().equals(LogicOp.AND)) return binaryFormula_;
		return super.visit((Node) binaryFormula_);
    }
    
    public Object visit(NegFormula negFormula_) {
	// can't do eq reasoning inside a NOT
	return negFormula_;
    }
    
    public Object visit(ComprehensionExpr comprehensionExpr_) {
	// can't do eq reasoning inside a comprehension
	return comprehensionExpr_;
    }
    
    public Object visit(ImplicationFormula implicationFormula_) {
	// can't do eq reasoning inside an implication
	return implicationFormula_;
    }
    
}
